We have investigated the magnetic behavior of a YBa 2Cu 3O 7 single crystal by measuring the harmonic components of its response to an alternating magnetic field and by monitoring directly the time-dependent signal produced in the AC susceptometer secondary coil. We are able to investigate up to the seventh-harmonic component and reconstruct the magnetic hysteresis loop. These measurements demonstrate a new approach to clarify the AC susceptibility behavior of high- T c superconductors.